High frequency electroacupuncture induced changes of IP3 level in rat brain and spinal cord

In the present study, the radioreceptor binding method was used to determine the changes of IP3 content in rat brain and dorsal spinal cord of high frequency (100 Hz) electroacupuncture (EA) analgesia and EA tolerance rat. The control levels of IP3 in rat brain (less cerebellum and cortex) and dorsal spinal cord were 6.3 +/- 0.78 pmol/mg protein and 3.4 +/- 0.60 pmol/mg protein, respectively. The results showed that IP3 in brain increased gradually within 45 min after stimulation in EA analgesia rat. Meanwhile, the dorsal spinal cord IP3 content decreased significantly 15 min, 30 min after EA stimulation and recovered to control level 45 min after EA stimulation. In EA tolerance rat, IP3 contents markedly increased in brain. And IP3 content in the spinal cord also increased dramatically within 30 min, but decreased rapidly to control level 45 min after EA stimulation. The IP3 level in EA tolerance rat brain and spinal cord was much higher than that in EA analgesia rat (P < 0.01). The studies first reported that high frequency (100 Hz) EA may be linked to PI system in its signal transduction pathways.